The present invention relates to a laser radiation device, and in particular, to a laser radiation device which employs a fiber laser that is capable of emitting a laser beam including two or more wavelength components.
Laser radiation devices for radiating objects with laser beams have widely been brought to practical use today in the fields of metal processing, semiconductor processing, medical care, etc. In almost laser radiation devices, a laser capable of emitting a laser beam including only one wavelength component is employed. Interaction between a laser beam and an object (metal, a semiconductor, a living body, etc.) depends on the wavelength of the laser beam, therefore, the oscillation wavelength of a laser radiation device is determined and selected depending on which interaction is desired. The absorption coefficient of a living body varies depending on parts (protein, fat, bone, water, etc.) of the living body. For instance, a 2 xcexcm band laser beam is known to be suitable for coagulation of soft tissue, a 9 xcexcm band laser beam is known to be suitable for perforation of dentin, a 3 xcexcm band laser beam is known to be suitable for precise incision, and a 10 xcexcm band laser beam etc. are known to be suitable for normal incision. A surgical laser knife which is provided with a 10 xcexcm band CO2 laser oscillator is in practical use today. As described above, laser radiation devices which are capable of emitting a laser beam including only one wavelength component have been used in almost cases. However, in the field of surgical laser knives, for example, it is also possible to implement and use a laser radiation device that is capable of emitting a laser beam including two or more wavelength components so that two or more effects can be attained simultaneously.
FIG. 1 is a schematic diagram showing a conventional laser radiation device which can be employed for emitting a laser beam including two or more wavelength components. The laser radiation device 31 shown in FIG. 1 includes a first laser device 21, a first collimator lens 23, a second laser device 24, a second collimator lens 26, a dichroic mirror 27, a total reflection mirror 29, and a focusing lens 30.
The first laser device 21 and the second laser device 24 having different oscillation frequencies emit a first laser beam 22 and a second laser beam 25 respectively. The first laser beam 22 and the second laser beam 25 emitted by the laser device 21 and 24 respectively are shaped into collimated beams by the first collimator lens 23 and the second collimator lens 26 respectively so as to be propagated in fixed directions losslessly, coupled together by the dichroic mirror 27, guided (reflected) by the total reflection mirror 29, and applied to an object 11 through the focusing lens 30. The characteristics of the two wavelength components (i.e. the first laser beam 22 and the second laser beam 25), such as the intensity, can be varied by controlling the first laser device 21 and the second laser device 24 respectively. The dichroic mirror 27 has high transmission (transmissivity) for the first laser beam 22 and high reflectivity for the second laser beam 25.
In the case where the above laser radiation device 31 is employed for a surgical laser knife, coupling of a 3 xcexcm band laser beam (which is suitable for precise incision of a living body) with a 2 xcexcm band laser beam (which is suitable for tissue coagulation and hemostasis by means of denaturalization of protein) is a desirable selection. In such a case, an Er (erbium)-doped YAG (yttrium aluminium garnet) crystal laser having an oscillation frequency of 2.94 xcexcm which is pumped by a 970 nm laser diode can be employed as the first laser device 21, and a Tm (thulium)-Ho(holmium)-co-doped YLF (yttrium lithium fluoride) crystal laser having an oscillation frequency of 2.06 xcexcm which is pumped by a 790 nm laser diode can be employed as the second laser device 24. If it is necessary to further couple a third laser beam (generated by another laser device having another oscillation frequency) to the coupled laser beam 28, the coupling can be attained by adding a coupling means which is similar to the dichroic mirror 27.
As described above, it is possible to exert two or more effects (each of which is characteristic of each wavelength component) on the object simultaneously, by employing the laser radiation device 31 employing the two laser devices 21 and 24 to the surgical laser knife. It is also possible to change characteristics of each wavelength component (such as the intensity) by controlling the two laser devices 21 and 24 depending on the characteristics of the object and desired effects, therefore, the intensity of each wavelength component in the coupled laser beam can be set optimally by controlling the two laser devices 21 and 24 respectively.
However, in the case where two or more different laser beams are coupled together and guided in the same direction, the optical axes of the laser beams having different wavelengths can have misalignment in the coupling. Further, the propagation characteristics of each wavelength component varies depending on the laser device that emitted the wavelength component, and thus misalignment and variations in the intensity can occur on the object especially when the laser beams are focused on the object. Furthermore, the laser beams generated and emitted by the laser radiation device are not necessarily visible, and thus it is not easy to check and adjust the positions of the focused laser beams (focused laser beam spots) on the object. Moreover, the above laser radiation device needs to be provided with two or more laser devices, therefore, the cost necessary for the laser beam sources (principle parts of the laser radiation device) becomes twice, the power consumption becomes large, and the size of the laser radiation device is necessitated to be large.
It is therefore the primary object of the present invention to provide a laser radiation device which is capable of generating and emitting a laser beam including two or more wavelength components and applying the two or more wavelength components to the object coaxially in uniform and stable irradiation conditions.
Another object of the present invention is to provide a laser radiation device which is capable of generating and emitting a laser beam including two or more wavelength components and applying the two or more wavelength components to the object, which can be realized with a low manufacturing cost, small running costs, and in a small size.
Another object of the present invention is to provide a laser radiation device which is capable of generating and emitting a laser beam including two or more wavelength components and applying the two or more wavelength components to the object, by which the user of the laser radiation device can easily see and recognize the irradiation point (i.e. a focused beam spot) of the laser beam on the object.
In accordance with a first aspect of the present invention, there is provided a laser radiation device comprising a pumping light emission means, a fiber laser means and a beam guiding means. The pumping light emission means generates and emits pumping light. In the fiber laser means, an optical fiber doped with laser ions is excited by the pumping light emitted by the pumping light emission means, and thereby a laser beam including two or more wavelength components is generated. The beam guiding means guides the laser beam generated by the fiber laser means into desired place and direction.
In accordance with a second aspect of the present invention, in the first aspect, the laser radiation device further comprises a beam shaping means for shaping the laser beam guided by the beam guiding means.
In accordance with a third aspect of the present invention, in the second aspect, the beam shaping means focuses the laser beam so that a focused laser beam including the two or more wavelength components will be applied to the object.
In accordance with a fourth aspect of the present invention, in the second aspect, the beam shaping means controls the shapes and/or areas of beam spots of the wavelength components on the object independently.
In accordance with a fifth aspect of the present invention, in the first aspect, the laser radiation device further comprises a beam modulation means for modulating optical characteristics of each of the wavelength components included in the laser beam.
In accordance with a sixth aspect of the present invention, in the fifth aspect, the beam modulation means includes one or more optical filters which can change the powers of one or more of the wavelength components.
In accordance with a seventh aspect of the present invention, in the first aspect, the beam guiding means includes two or more reflection means which are arranged in a multiple-joint arm configuration.
In accordance with an eighth aspect of the present invention, in the first aspect, the beam guiding means is implemented by a guiding optical fiber.
In accordance with a ninth aspect of the present invention, in the first aspect, the beam guiding means is implemented by the optical fiber of the fiber laser means.
In accordance with a tenth aspect of the present invention, in the first aspect, the laser radiation device further comprises a pointing beam emission means. The pointing beam emission means generates and emits a pointing beam for indicating the optical axis of the laser beam or the irradiation point of the laser beam on the object.
In accordance with an eleventh aspect of the present invention, in the tenth aspect, the laser radiation device further comprises a pointing beam coupling means for coupling the pointing beam emitted by the pointing beam emission means with the laser beam coaxially.
In accordance with a twelfth aspect of the present invention, in the eleventh aspect, the pointing beam coupling means is implemented by a total reflection element of the beam guiding means which transmits the pointing beam while reflecting the laser beam.
In accordance with a thirteenth aspect of the present invention, in the eleventh aspect, the pointing beam coupling means is implemented by an optical coupler which is attached to a guiding optical fiber which implements the beam guiding means.
In accordance with a fourteenth aspect of the present invention, in the tenth aspect, one or more of the wavelength components of the laser beam generated by the fiber laser means are visible beams, and one or more of the visible beams are used as the pointing beam.
In accordance with a fifteenth aspect of the present invention, in the tenth aspect, the laser radiation device further comprises a pointing beam reflection monitoring means. The pointing beam reflection monitoring means monitors the status of the object at the irradiation point in real time, by monitoring the intensity of the reflection of the pointing beam from the irradiation point.
In accordance with a sixteenth aspect of the present invention, in the first aspect, one or more kinds of rare-earth ions are doped in the optical fiber of the fiber laser means as the laser ions.
In accordance with a seventeenth aspect of the present invention, in the first aspect, the pumping light emission means includes one or more light sources and generates and emits the pumping light that includes two or more wavelength components.
In accordance with an eighteenth aspect of the present invention, in the first aspect, the optical fiber of the fiber laser means is doped with holmium ions and thulium ions.
In accordance with a nineteenth aspect of the present invention, in the first aspect, the optical fiber of the fiber laser means is doped with holmium ions as laser ions, and an optical fiber doped with thulium ions is connected to the optical fiber of the fiber laser means for emitting a 480 nm band pointing beam for indicating the optical axis of the laser beam or the irradiation point of the laser beam on the object.
In accordance with a twentieth aspect of the present invention, in the first aspect, holmium ions are doped in the optical fiber of the fiber laser means as the laser ions, and the pumping light emission means generates and emits the pumping light that includes 890 nm band pumping light and/or 1.1 xcexcm band pumping light, and the laser beam emitted by the optical fiber of the fiber laser means at least includes a 3 xcexcm band component and a 2 xcexcm band component.
In accordance with a twenty-first aspect of the present invention, in the twentieth aspect, the optical fiber of the fiber laser means further emits one or more laser beams and/or fluorescence of a 550 nm band and/or a 640 nm band.
In accordance with a twenty-second aspect of the present invention, in the first aspect, thulium ions are doped in the optical fiber of the fiber laser means, and the laser beam emitted by the optical fiber of the fiber laser means at least includes two or more wavelength components and a laser beam or fluorescence of a 480 nm band.